I found it! I knew I had read somewhere in one of my speed books about the PCV system connected to exhaust rather than intake - see attached. Also, this other extract below is taken, believe it or not, from the Wikipedia page about PCV valves:
'Not all petrol engines have PCV valves. Dragsters sometimes use a scavenger system and venturi tube in the exhaust to draw out combustion gases and maintain a small amount of vacuum in the crankcase to prevent oil leaks on to the race track.'
'Not all petrol engines have PCV valves. Dragsters sometimes use a scavenger system and venturi tube in the exhaust to draw out combustion gases and maintain a small amount of vacuum in the crankcase to prevent oil leaks on to the race track.'